Subsurface pump



June 9, 1964 R. 1.. CHENAULT 3,136,265

SUBSURFACE PUMP Filed Oct. 12, 1962 2w 0 mm mm Pltk 4- INVENTOR. R0) L. CHEN/JUL T M5 Ilium Attorney United States Patent SUBSURFACE PUMP Roy L. Chenault, Dallas, Tex., assignor to United States Steel Corporation, a corporation of New Jersey Filed Oct. 12, 1962, Ser. No. 230,189 2 Claims. (Cl. 103-179) This invention relates to improved subsurface pumps particularly for handling heavy viscous oils or for use in slanted wells.

In some oil wells there is a substantial resistance to downward movement of the rod string during a downstroke of the pump. As a result, the pump plunger may not travel downwardly as rapidly as the drive at the surface is operating. The length of the pump stroke at the bottom is diminished with loss of efliciency. The rod string must sustain a compressive load during each downstroke, resulting in severe stresses and stress reversals therein. This condition may arise, for example, in wells which produce heavy viscous oils or in slanted wells Where rod friction is high.

An object of the present invention is to provide improved subsurface pumps which overcome the foregoing difliculties by avoiding or minimizing compressive loads on the rod string during a downstroke.

A further object is to provide improved subsurface pumps which remove or diminish upward forces on the reciprocating parts during a downstroke, thereby relieving the rod string of compressive loads.

In the drawing:

FIGURE 1 is a diagrammatic vertical section of a subsurface pump constructed in accordance with one embodiment of my invention;

FIGURE 2 is a similar view showing a modification;

FIGURE 3 is a fragmentary vertical section showing an alternative support means for the pump barrel; and

FIGURE 4 is a diagrammatic vertical section of surface equipment which I can use with the pumps shown in FIGURES 1 and 2.

The pump shown in FIGURE 1 comprises a stationary barrel and a reciprocable plunger 12 fitted in said barrel. The plunger has a vertical bore 13, and it carries a traveling intake valve 14 at the top of the bore. A valve cage 15 is fixed to the top of the plunger to confine this valve. A valve rod 16 is fixed to the top of the cage and extends upwardly therefrom. The upper portion of the barrel has a head 17 which closely receives the valve rod. The head also contains a vertical passage 18 and it carries a valve 19 confined in a cage 20 at the top of this passage. I attach the upper end of the barrel to a conventional well tubing 21. The lower end of the barrel is open (no standing valve). I attach the upper end of the valve rod 16 to a conventional sucker rod string 22 through a coupling 23.

In operation, a drive mechanism at the surface alterqately lowers and raises the rod string 22, valve rod 16 and plunger 12. As the plunger makes a downstroke, the intake valve 14 opens to admit well fluid to the space within barrel 10 above the plunger. The pressure of the fluid column in tubing 21 closes valve 19. Thus the head 17 and valve 19 cooperate to confine the tubing pressure above head 17 during a downstroke, whereby the lower end of the valve rod is subjected only to the intake pressure. If the valve rod 16 and rod string 22 have equal cross-sectional areas, the forces resulting from pressure in the tubing and acting downwardly on the rod string balance the forces acting upwardly. The full force resulting from the effective weight of the rods assists in lowering the plunger, and the rod string is substantially free of any compressive load. If the valve rod has a larger cross sectional area than the rod string, the pressure of the 3,136,265. Patented June 9, 1964 fluid column exerts a net downward force on the valve rod and thus actually tensions the rod string. If the valve rod has the smaller cross-sectional area, the flu d column exerts a net upward force, but the magnitude is proportional only to the difference in area between the rod string and the valve rod. As the plunger makes an upstroke, valve 14 closes and valve 19 opens. Thus the plunger forces fluid from the barrel up the tubing to the surface.

FIGURE 2 shows a modified pump which comprises a barrel 10, a plunger 12 having a bore 13, a traveling intake valve 14 and a cage 15, all similar to the corresponding parts of the embodiment shown in FIGURE 1. A tube 25 is fixed to the top of the cage and extends upwardly therefrom. Tube 25 has ports 26 adjacent its lower end and ports 27 adjacent its upper end, and it contains a valve 28 located between the upper and lower ports. The upper portion of the barrel has a head 29 which closely receives the outside of tube 25. I attach the upper end of the barrel to a conventional tubing 21, and I attach the upper end of tube 25 to a conventional rod string 22, as in the first embodiment. The operation of the pump shown in FIGURE 2 is similar to the first embodiment, with valve 28 replacing valve 19. Tube 25 has a larger cross-sectional area than the rod string 22. Hence during a downstroke the fluid column in tubing 21 always exerts a net downward force on tube 25 and thus tensions the rod string. The diameter of tube 25 can be made larger or smaller to increase or diminish the downward force with a given fluid pressure in the tubing.

FIGURE 3 shows diagrammatically an alternative support means for the pump barrel 10 applicable to either embodiment of pump just described. The tubing 21a of FIGURE 3 has a shoulder 30 near the bottom. A sealing cup or ring 31 is fixed to the outside of the barrel and held in place by a nut 32. The nut provides a shoulder which rests on the shoulder 30 in the tubing. This type of pump is known as an insert or rod-type pump and is run into a well on the sucker rods.

FIGURE 4 shows surface equipment which I can use to advantage with the pump shown in FIGURE 2 or with the pump shown in FIGURE 1, provided the valve rod 16 has a larger cross-sectional area than the rod string 22. As FIGURE 4 shows, the tubing 21 has a stufliing box 35 at its upper end. A conventional polished rod 36 is attached to the upper end of the rod string 22 and extends through the stuffing box to a suitable drive not shown. I connect a flow line 37 to the tubing near its upper end and connect a gas accumulator 38 to the flow line. I also connect an adjustable back pressure valve 39 and a pressure gauge 40 to the fiow line. With this arrangement I can adjust the back pressure valve to add any desired pressure to the fluid column at the surface in the event the static head of the column is insutlicient to lower the plunger at the desired rate with the dimensions originally selected for the plunger 12, rod 22 and tube 25. The gas accumulator 38 serves to maintain a nearly uniform back pressure throughout a stroke. Most oil wells produce sufficient gas with the well fluid to maintain the accumulator fully charged, but the accumulator can be charged through a valve 41 if necessary.

From the foregoing description it is seen that my invention affords pump mechanisms of simple construction which eifectively avoid compressive loads on the rod string during a downstroke. My invention makes it possible to apply any desired tension load in a rod string to prevent stress reversals and to increase operating speeds in viscous fluids and/ or slanted holes where excessive rod friction may interfere with movement of the pump plunger. Thus my invention improves the efiiciency over conventional pumps where there is a problem of resistance to downward movement, and also relieves the rod string of undesirable stress reversals which promote fatigue H failures of sucker rods.

While I have shown and described certain preferred embodiments of my invention, it is apparent that other modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim: T

1. A subsurface pump installation comprising a well tubing, a sucker rod string extending from the surface through said tubingand adapted to move up and down, a pumpbarrel supported at its upper end on said tubing and being open at its lower end, a plunger housed within said barrel, a traveling intake check valve carried by said plnngen an upwardly extending valve rod fixed to said plunger and attached at its upper end to said rod string, a head closing the upper end of said barrel above said plunger and closel receiving said valve rod, and a check valvefmounted in said head, said head and said second:

4 named valve cooperating to prevent pressure of the fluid column in said tubing from acting upwardly on said rod string during a downstroke, said valve rod being of larger cross-sectional area than said rod string to assure that the fluid column exerts a net downward force on the valve rod during a downstroke, thereby avoiding compressive stresses on the rod string.

2. A pump installation as defined in claim 1 including means at the surface for adding pressure to the fluid column in the well tubing and adding to the force which acts downwardly on the rod string.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A SUBSURFACE PUMP INSTALLATION COMPRISING A WELL TUBING, A SUCKER ROD STRING EXTENDING FROM THE SURFACE THROUGH SAID TUBING AND ADAPTED TO MOVE UP AND DOWN, A PUMP BARREL SUPPORTED AT ITS UPPER END ON SAID TUBING AND BEING OPEN AT ITS LOWER END, A PLUNGER HOUSED WITHIN SAID BARREL, A TRAVELING INTAKE CHECK VALVE CARRIED BY SAID PLUNGER, AN UPWARDLY EXTENDING VALVE ROD FIXED TO SAID PLUNGER AND ATTACHED AT ITS UPPER END TO SAID ROD STRING, A HEAD CLOSING THE UPPER END OF SAID BARREL ABOVE SAID PLUNGER AND CLOSELY RECEIVING SAID VALVE ROD, AND A CHECK VALVE MOUNTED IN SAID HEAD, SAID HEAD AND SAID SECONDNAMED VALVE COOPERATING TO PREVENT PRESSURE OF THE FLUID COLUMN IN SAID TUBING FROM ACTING UPWARDLY ON SAID ROD STRING DURING A DOWNSTROKE, SAID VALVE ROD BEING OF LARGER CROSS-SECTIONAL AREA THAN SAID ROD STRING TO ASSURE THAT THE FLUID COLUMN EXERTS A NET DOWNWARD FORCE ON THE VALVE ROD DURING A DOWNSTROKE, THEREBY AVOIDING COMPRESSIVE STRESSES ON THE ROD STRING. 